Writing the Equation to an Unknown Function?

Question

I play a game that utilizes bombers to attack troops on a planet. The bombers takea percentage of the population depending on how many bombers were present in the battle. I was able to easily figure out the percentages for various fleet sizes. My question is how could I use the data I collected to write an equation that can accurately determine the number of bombers needed to destroy a given percentage. The data looks like a log function or possible a radical function when graphed. I attempted to solve the problem as if it was a log function but came up empty handed. Is there anyway to use the data to determine the equation the game is using or write my own to estimate. I can provide data if necessary but am not sure what I'm trying to do is possible.